ANALYSIS ON THE UPINTRUSION OF THERMAL FLUID AND THE MIGRATION AND ACCUMULATION RULES OF NATURAL GAS AND CO₂ IN THE MUD DIAPIRS OF THE YINGGEHAI BASIN

The Yinggehai Basin is a Cenozoic high-heat basin developed on the passive continental margin of the northern part of the South China Sea.Its high geotemperature field and high geothermal flux are mainly concentrated in the mud-diapir structural zone of the Yinggehai Depression in the central part of the basin.So,the upintrusion of thermal fluid in the mud diapirs,especially the thermal fluid action in the late stage controlled the migration,accumulation and enrichment rules of natural gas and CO₂.Meanwhile,the local intrusion of thermal fluid by different layers,different blocks and different districts resulted in the migration,accumulation and enrichment differences of crust-sourced CO₂ and hydrocarbon gases and the characters of local enrichment by different layers,different blocks and different districts.In a word,the upintrusion of thermal fluid in the mud diapirs was the key factor controlling the migration and accumulation of natural gas and CO₂.According to the geochemical characteristics of CO₂ and hydrocarbon gases and their controlling factors,the migration and accumulation rules of CO₂ and hydrocarbon gases can be analysed and predicted.This will provide decision basis for the exploration of natural gas.